• Most ingest organic materials
  • consume, breakdown internally with enzymes

• Lack structural support from cell walls
  • extracellular proteins connect and strengthen cells
  • most abundant are collagen (not found in plants/fungi)

• Cells organized into tissues
  • similar cells acting as a functional unit
  • muscle & nervous tissue allows animals to move

• Body plan = programmed development driven by evolution

• Fertilized zygote undergoes cleavage
  • mitotic cell divisions without cell growth
  • rapid division but overall size stays same

• Early multicellular stage called a blastula (hollow ball)
  • protostome vs deuterostome = alignment of cells

• Germ layers develop in next stage (gastrulation)
  • develop into body parts

• Many animals have larval and adult stage
  • larva are sexually immature
  • larva look, live and eat differently

• Blastopore: opening of central cavity of an embryo

• In most animals a second opening forms at opposite end
  • become openings of digestive tube

• Protostomes: blastopore becomes mouth
• Deuterostomes: blastopore becomes anus

• Sponges (0), Diploblasts (2), Triploblasts (3)
  • germ layers develop into tissues and organs

• Ectoderm:

• Endoderm:

• Mesoderm:

• Coelom:

• Fluid/air spaces between mesoderm layers
  • digestive track and body wall

• Body cavity called coelom
  • cushions organs
  • fluid resistance for muscles
  • allows organs to move independently

• Not all triploblasts have a coelom

• The dorsal cavity and the ventral cavity are the largest body compartments.

• Dorsal body cavity includes the cranial cavity, enclosed by the skull, and the spinal cavity, enclosed by the spine

• Ventral body cavity subdivided into 2 compartments
  • vental contains the lungs and heart
  • abdominopelvic contains the kidneys, ureters, stomach, intestines, liver, gallbladder, pancreas, bladder, anus and reproductive system

• Animal body plans are expressions of the genome, but the product of millions of years of evolution

• Animals body plans are constrained by physical laws
  • diffusion, movement, heat exchange
  • gravity

• Example: Properties of water and animal shape
  • water more dense = surface bumps cause drag
  • natural selection favored tapered smooth bodies
  • convergent selection across aquatic mammals

• Animals must uptake nutrients, lose waste and exchange gases
  • occurs across plasma membrane of cells

• Simple internal body plan: Hydra
  • body wall and cavity open to environment
  • gastrovascular cavity

• Animals must uptake nutrients, lose waste and exchange gases
  • occurs across plasma membrane of cells

• Body plan optimized for surface area: tapeworms
  • thin, flat shape
  • lots of outer cells exposed to environment

• Animals must uptake nutrients, lose waste and exchange gases
  • occurs across plasma membrane of cells

• Many animals (like humans) have more complex internal bodies
  • reduces total # of cells on outer surface
  • volume > surface area
  • ‘think’ whale versus flea

• Internal structures for exchange evolve…
  • highly branched or folded

• Animals must uptake nutrients, lose waste and exchange gases
  • occurs across plasma membrane of cells

• Many animals (like humans) have more complex internal bodies
  • reduces total # of cells on outer surface
  • ‘think’ whale versus flea

• Internal organs for exchange evolve…
  • highly branched or folded
  • digestion, respiration and circulation
  • fluids connect structures to other cells

• External skeleton?

• Sensory organs (eyes, ears, etc.)?

• Internal digestion organs?

• Specialized filtration systems?

• How do internal systems allow life on land?